[Bibby C, Jones M & Marsden S 1 999: Expedition field techniques. Bird surveys. Royal Geographical Society, London, 1 37.]Search in Google Scholar
[BirdLife International 201 3: Species factsheet: Aquila heliaca. Downloaded from http://www.birdlife.org on 1 7. October 201 3.]Search in Google Scholar
[Bondev Z 1 991 : Flora na Bylgaria [Flora in Bulgaria]. Publishing House “Kliment Ohridsky”, Sofia, 1 84. [In Bulgarian] ]Search in Google Scholar
[Demerdzhiev D 2011 : Iztochniyat tsarski orel (Aquila heliaca heliaca Savigny, 1 809) (Accipitridae - Aves) v Balgariya - razprostranenie, biologiya, ekologiya, chislenost i merki za opazvane [Eastern imperial eagle (Aquila heliaca heliaca Savigny, 1 809) (Accipitridae - Aves) in Bulgaria - distribution, biology, ecology, numbers, and conservation measures]. Synopsis of the PhD. thesis. BASNMNH, Sofia, 39. [In Bulgarian] ]Search in Google Scholar
[Demerdzhiev D 2014a: Factors influencing bird mortality caused by power lines within Special Protected Areas and undertaken conservation efforts. Acta zoologica Bulgarica Supplementum 5: in print.]Search in Google Scholar
[Demerdzhiev D 2014b: Conservation status and dynamics of the avifauna of Bessaparski Hills SPA: general review. Acta zoologica Bulgarica Supplementum 5: in print.]Search in Google Scholar
[Demerdzhiev D, Horváth M, Kovács A, Stoychev S & Karyakin I 2011 .: Status and population trend of the eastern imperial eagle (Aquila heliaca) in Europe in the period 2000-201 0. Acta zoologica Bulgarica Supplementum 3: 5-1 4.]Search in Google Scholar
[Demerdzhiev D, Gradev G, Stoychev S, Ivanov I, Petrov T & Marin S 2011 b: Increase of the population of the eastern imperial eagle (Aquila heliaca) in Bulgaria. Acta zoologica Bulgarica Supplementum 3: 41-54.]Search in Google Scholar
[Demerdzhiev D, Stoychev S, Petrov T, Angelov I & Nedyalkov N 2009: Impact of power lines on bird mortality in southern Bulgaria. Acta zoologica Bulgarica 61 (2): 1 77-1 85.]Search in Google Scholar
[Ferrer M 2001 : The Spanish imperial eagle. Lynx Edicions, Barcelona, 224.]Search in Google Scholar
[Ferrer M & Penteriani V 2008: Non-independence of demographic parameters: positive density-dependent fecundity in eagles. Journal of Applied Ecology 45: 1 453-1 459. DOI: 1 0.1111 /j.1 365-2664.2008.-01 497.x.]Search in Google Scholar
[Forsman D 2005: Eastern imperial eagle plumages. Alula 4: 1 47-1 52.]Search in Google Scholar
[Galabov Z 1 982: Fiziogeografski rayoni [Physiographic regions], 11 5-21 5. In: Galabov Z (ed), Geografiya na Balgariya , tom 3. Fiziogeografiya [Geography of Bulgaria, vol. 3. Physiography]. BAS, Sofia, 31 5. [In Bulgarian] ]Search in Google Scholar
[Gerdzhikov G & Demerdzhiev D 2009: Data on bird mortality in “Sakar” SPA (BG021 ), caused by hazardous power lines. Ecologia Balkanica 1 : 67-77.]Search in Google Scholar
[Gonzalez LM 1 991 : [Natural history of the Spanish imperial eagle (Aquila adalberti Brehm, 1 861 )].]Search in Google Scholar
[Colección Téchnica, ICONA, Madrid. [In Spanish] ]Search in Google Scholar
[Hernández-Matías A, Real J & Pradel R 2011 : Quick methods for evaluating survival of age-characterizable long-lived territorial birds. Journal of Wildife Management 75: 856-866. DOI: 1 0.1 002/jwmg.1 02.10.1002/jwmg.102]Search in Google Scholar
[Horváth ., Demeter I, Fatér I, Firmánszky G, Kleszó A, Kovács A, Szitta T, Tóth I, Zalai T & Bagyura J 2011 : Population dynamic of the Imperial Eagle (Aquila heliaca) in Hungary between 2001 and 2009. Acta zoologica Bulgarica Supplementum 3: 61-70.]Search in Google Scholar
[Lack DL 1 954: The natural regulation of animal numbers. Oxford University Press, London, 343.]Search in Google Scholar
[Meyburg B-U 1 974: Sibling aggression and mortality among nesting eagles. Ibis 11 6: 224-228.10.1111/j.1474-919X.1974.tb00243.x]Search in Google Scholar
[Meyburg B-U & Garzon J 1 973: Sobre la protección del Aguila Imperial Ibérica Aquila heliaca adalberti aminorando artificialmente la mortalidad juvenil. Ardeola 1 9: 1 07-1 28.]Search in Google Scholar
[Newton I 1 979: Population ecology of raptors. T & AD Poyser, Berkhamsted, UK, 432.]Search in Google Scholar
[Penteriani V, Otalora F & Ferrer M 2005: Floater survival affects population persistence. The role of prey availability and environmental stochasticity. Oikos 1 08: 523-534. DOI: 1 0.1111 /j.0030-1 299.2005.-1 351 4.x.]Search in Google Scholar
[Petrov T & Stoychev S 2002: Natsionalen plan za deystvie za tsarskiya orel (A. heliaca) v Balgariya [National Action Plan for the imperial eagle (A. heliaca)], 1 32-1 61 . In: Iankov P (ed), Global threatened birds in Bulgaria. National Action plans for the conservation. Part 1 . BSPB-MOSV, Conservation Series, Book 4, BSPB, Sofia, 227. [In Bulgarian] ]Search in Google Scholar
[Roth T & Amrhein V 201 0. Estimating individual survival using territory occupancy data on unmarked animals. Journal of Applied Ecology 47: 386-392. DOI: 1 0.1111 /j.1 365-2664.201 0.01 786.x.]Search in Google Scholar
[Shapiro S, Wilk M & Chen H 1 968: A comparative study of various tests of normality. Journal of the American Statistical Association 63: 1 343-1 372.]Search in Google Scholar
[StatSoft 2004: STATISTICA (data analysis software system), version 7. www.statsoft.com.]Search in Google Scholar
[Stoychev S, Ivanov I, Petrov T, Marin S, Demerdzhiev D, Gradev G & Domuschiev D 2004: Status of the eastern imperial eagle (Aqila heliaca) in Bulgaria between 1 994 and 2002, 653-660. In: Chancellor RD & Meyburg B-U (eds), Raptors worldwide. Proceedings of the VI world conference on birds of prey and owls. Budapest, Hungary 1 8-23 May 2003World Working Group on Birds of Prey and Owls & MME/BirdLife Hungary, Berlin & Budapest, 867.]Search in Google Scholar
[Stoychev S & Karafeizov T 2004: Power line design and raptor protection in Bulgaria, 443-451 . In: Chancellor RD & Meyburg B-U (eds), Raptors worldwide. Proceedings of the VI world conference on birds of prey and owls. Budapest, Hungary 1 8-23 May 2003World Working Group on Birds of Prey and Owls & MME/BirdLife Hungary, Berlin & Budapest, 867.]Search in Google Scholar
[Svehlik J & Meyburg B-U 1 979: Gelegegröbe und Bruterfolg des Schreiadlers (Aquila pomarina) und des Kaiseradlers (Aquila heliaca) in den ostslowakischen Karpaten 1 966-1 978. Journal für Ornithologie 1 20: 406-41 5.]Search in Google Scholar
[Stoytchev S, Demerdzhiev D & Petrov T 201 2: Action plan for the conservation of imperial eagle (Aquila heliaca) in Bulgaria. MEW, Sofia, 71 .]Search in Google Scholar
[Vasic V & Misirlic R 2002: The eastern imperial eagle (Aquila heliaca) in Yugoslavia with reference to F.Y.R. Macedonia. Aquila 1 07-1 08: 1 45-1 69.]Search in Google Scholar
[Voos K 1 960: Atlas of European birds. Nelson, Edinburgh, 284.]Search in Google Scholar
[Zhelev P, Gradev G, Ivanov I & Georgiev D 2009: Materiali vyrhu hranitelniat spektyr na carskiat orel v Yjna Bylgaria [Materials on the food spectrum of imperial eagles (Aquila heliaca, Savigny, 1 809) in southern Bulgaria]. Ecologia Balkanica 1 : 51-58. [In Bulgarian] ]Search in Google Scholar